|448. Kong, J.; Schmalz, Th.; Motz, G.; Müller, A.H.E.: Magnetoceramic Nanocrystals from Bulk Pyrolysis of Novel Hyperbranched Polyferrocenyl(boro)carbosilanes, J. Mater. Chem. 1(7), 1507-1514 (2013) -- DOI: 10.1039/C2TC00193D|
We report a novel strategy to synthesize nanostructured magnetoceramics via a direct bulk pyrolysis of hyperbranched polycarbosilanes without any assistance of nanoscaled templates. The hyperbranched polyferrocenyl(boro)carbosilanes (hb-PBCS) were synthesized via a convenient A2+B3 strategy. After the pyrolysis of hb-PBCS under a nitrogen atmosphere and 1100 °C, iron silicide nanocrystals enriched ceramics with grain size of 20-60 nm were formed. The regular architecture and quite higher ceramic yield of polymeric precursors are superior to retaining iron and silicon that give a possibility to aggregate into regular nanocrystals during the bulk pyrolysis in comparison to their linear counterparts. Furthermore, if the mixed precursor of a hb-PBCS with regular architecture and a silylene-diacetylene polymer with high ceramic yield was employed, a hierarchical structure of uniform nanorods with diameters of 20-30 nm and aspect ratios of ~5 together with microspheres with diameters of 4-8 μm could be obtained under the same pyrolytic condition. A vibrating sample magnetometer measurement demonstrated that the generated iron silicide nanocrystals enriched ceramics possessed weak ferromagnetism with an ultra low hysteresis loss.